The invention relates to methods and apparatus for transporting sewage in a vacuum system.
In the publication EP 0 333 045 there is disclosed a method for transporting sewage from a source of sewage through a sewer network to a sewer or collecting container. The transport takes place by means of and through a liquid ring pump, whereby the liquid ring pump is on-line with the sewer network or sewer piping. This known solution is, however, susceptible to disturbances and requires additional means for ensuring its function. The liquid ring pump has a complicated structure and it is easily damaged and furthermore it constantly requires additional water for maintaining the liquid ring as well as for for cooling. The additional means and the components related thereto increase room requirement and increase weight, whereby the locations where the known solution can be used are defined by the availability of additional room and by limitations caused by the additional weight.
The object of the present invention is to achieve a method, by which the above mentioned disadvantages are avoided and which provides an efficient operation of the vacuum system by simple means.
The invention is based on the idea to achieve a compact solution, which can be used for transporting sewage during the vacuum phase as well as during the subsequent transporting phase. The solution also has to have tolerance with regard to the composition and quality of the sewage. This object is attained by using a rotary lobe pump arranged on-line with the sewer piping as a transport means.
The invention advantageously employs two rotary lobe pumps, which may be operated alternately, at the same time or independently of each other for generating vacuum in the sewer piping. This provides for example for keeping the wear of the pumps equal and for ensuring additional capacity for vacuum generation.
By defining the control of the rotary lobe pump so that it at a predetermined occurrence changes the direction of rotation of the rotary lobe pump, the pump can advantageously, in addition for generating vacuum, for example also be used for emptying sewage from a temporary collecting container or for removing a disturbance, for example a blockage, in the flow of the pump, whereby it is not necessary to stop the pump, which would have a decisive effect on the usability and function of the sewer piping.
The filling an emptying of the temporary collecting container is advantageously controlled by monitoring its filling degree.
Disturbances, for example the above mentioned blockages, in the through-flow of the rotary lobe pump, are advantageously monitored on the basis of the power consumption of the pump. A blockage temporarily raises the power consumption of the pump, whereby the direction of rotation of the pump may temporarily be changed for certain periods of timer to clear the blockage. This can be arranged to be repeated, for example 2 to 8 times. If the blockage is not removed at this stage, the pump can be stopped for required measures. The number of changes of the direction of rotation are as such not in any way limited.
The power consumption of the rotary lobe pump can advantageously be monitored for example by following the consumption of electric current of the electric motor of the pump.
The vacuum system is advantageously controlled by and its operating parameters are advantageously monitored by a control center.
The invention also relates to a vacuum system, the main characterising features of which are given in claim 9 and preferable embodiments in claims 10-17.